ios CoreData的使用记录(XCode 4.2)

1：导入CoreData的framework

 

2：AppDelegate类的头文件中

#import <CoreData/CoreData.h>

 

@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
@property (nonatomic, readonly) NSString *applicationDocumentsDirectory;

3：在AppDelegate的实现文件中

@synthesize managedObjectModel;
@synthesize managedObjectContext;
@synthesize persistentStoreCoordinator;
@synthesize applicationDocumentsDirectory;

- (void)dealloc
{
    [_window release];
    [_tabBarController release];
    [managedObjectModel release];
    [managedObjectContext release];
    [persistentStoreCoordinator release];
    [applicationDocumentsDirectory release];
    [super dealloc];
}

- (NSManagedObjectContext *)managedObjectContext
{
    if (managedObjectContext != nil) {
        return managedObjectContext;
    }
    
    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (coordinator != nil) {
        managedObjectContext = [[NSManagedObjectContext alloc] init];
        [managedObjectContext setPersistentStoreCoordinator:coordinator];
    }
    
    return managedObjectContext;
}

- (NSManagedObjectModel *)managedObjectModel 
{
    if (managedObjectModel != nil) {
        return managedObjectModel;
    }
    
    //从本地所有xcdatamodel文件中获得这个CoreData的数据模板
    managedObjectModel = [[NSManagedObjectModel mergedModelFromBundles:nil] retain];
    
    return managedObjectModel;
}

- (NSPersistentStoreCoordinator *)persistentStoreCoordinator 
{
    if (persistentStoreCoordinator != nil) {
        return persistentStoreCoordinator;
    }
    
    NSURL *storeUrl = [NSURL fileURLWithPath:[[self applicationDocumentsDirectory] stringByAppendingPathComponent:@"TestDB.sqlite"]];//数据库名为TestDB.sqlite
    
    NSError *error;
    persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    
    
    if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {
        NSAssert(0, @"persistentStoreCoordinator init failed!");
    }
    
    return persistentStoreCoordinator;
}

- (NSString *)applicationDocumentsDirectory
{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *basePath = ([paths count] > 0) ? [paths objectAtIndex:0] : nil;
    return basePath;
}
- (void)applicationWillTerminate:(UIApplication *)application
{
    /*
     Called when the application is about to terminate.
     Save data if appropriate.
     See also applicationDidEnterBackground:.
     */
    NSError *error;
    if (managedObjectContext != nil) {
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            NSAssert(0, @"save changes failed when terminage application!");
        }
    }
}

完成上述步骤之后，ViewController类里面就可以访问数据库了。

4: 建立数据库模型，如下选择新建文件->Core Data->Data Model

点击下一步输入上面确定的数据库名：TestDB

选中新产生的文件 TestDB.xcdatamodeld,右边的窗口将会变成编辑data model的，如下图点击Add Entity之后输入你要的表名。

完成之后它将出现在如下图（我这里表名是Event）。选中Event点击上图所示的Add Attribute就可以给表增加字段了。

当你把表和字段都建立好了之后。在new file，选择第2张图里面的NSManagedObject subclass。一路next下去。编译器将会自动给每张表生成对应的.h和 .m文件，这样数据模型就ok了。

5：插入数据

    CLLocation *location = [locationManager location];
    
    if (!location) {
        return;
    }
    
    Event *event = (Event *)[NSEntityDescription insertNewObjectForEntityForName:@"Event" inManagedObjectContext:managedObjectContext];
    
    CLLocationCoordinate2D coordinate = [location coordinate];
    [event setLatitude:[NSNumber numberWithDouble:coordinate.latitude]];
    [event setLongitude:[NSNumber numberWithDouble:coordinate.longitude]];
    [event setCreationDate:[NSDate date]];
    
    NSError *error = nil;
    if (![managedObjectContext save:&error ]) {
        // handle error
    }

6：查询数据：

    eventArray = [[NSMutableArray alloc] init];
    
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];
    [request setEntity:entity];
    //查询结果排序
   NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
    
    [request setSortDescriptors:sortDescriptors];
    [sortDescriptors release];
    [sortDescriptor release];
    
    
    NSError *error = nil;

    //NSMutableArray是一个Event对象的数组，这是有上面那条蓝色语句决定的。

    NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];
    
    if (mutableFetchResults == nil) {
        // Handle the error
    }
    
    [self setEventArray:mutableFetchResults];
    [mutableFetchResults release];
    [request release];

7：删除数据

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    //删除在indexPath处的managed object
    if (editingStyle == UITableViewCellEditingStyleDelete) {
        NSManagedObject *eventToDelete = [eventArray objectAtIndex:indexPath.row];
        [managedObjectContext deleteObject:eventToDelete];
    }
    
    //更新数组和table view
    [eventArray removeObjectAtIndex:indexPath.row];
    [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath ] withRowAnimation:YES];
    
    //提交改动
    NSError *error = nil;
    if (![managedObjectContext save:&error]) {
        //handle error
    }
}

更多资料请参考：

https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CoreData/cdProgrammingGuide.html#//apple_ref/doc/uid/TP40001075

转载：http://hi.baidu.com/excalibur/item/ba72fb0f73c9f1c32f4c6b36